Finding Earth's distant cousins might be harder than previously thought.
University of Toronto-Scarborough

Unpack your bags and defrost your shipboard cryogenic chamber. New research out Monday suggests that it may not be as easy to identify potentially habitable planets as recent discoveries might have led us to believe.

Without getting too much into the weeds of spectroscopy and astrobiology, the popular method of looking for planets in distant galaxies is to analyze the light from those parts of deep space in search of "biosignatures," spectral indicators that could demonstrate the presence of certain elements that typically accompany life, like methane or oxygen.

So when astronomers spy a planet like the recently publicized discovery of Kepler-186f which looks to be close in size to Earth, orbiting within the habitable zone of its star and showing possible biosignatures, there's reason to get excited.

But a team led by Hanno Rein at the University of Toronto at Scarborough has published findings in the Proceedings of the National Academy of Sciences that demonstrate certain conditions that could produce a false positive for a habitable exoplanet.

"According to a our study, a spectral signature suggestive of life on a planet outside our own solar system (exoplanet) could be spoofed by the combined light of a lifeless exoplanet and its lifeless exomoon," Rein wrote in an email to Crave.

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Rein suggests that to be able to spot more Earth-like planets with a high enough degree of certainty to rule out possible false positives would require a space telescope about 10 times larger than our largest telescopes, either in space or on Earth.

"Inferring a biosphere on an exoplanet might be beyond humanity's reach in the foreseeable future," Rein said.

At the moment, Earth-bound telescopes three times the size of our current largest scopes are planned, but indeed, nothing like what Rein suggests is on the horizon.

I've reached out to scientists at NASA for a reaction to Rein's research and will update this post when I hear back. Wesley Traub, a planetary scientist at NASA's Jet Propulsion Laboratory, told Science that Rein's false positive scenario would likely fool scientists.

Despite his skepticism of current methods, Rein says the search for life on planets is worthwhile, but thinks it might make more sense to focus on interesting spots in our own solar system. He also says the search for exoplanets should be broadened to search for planets around cooler stars, like the M-dwarf that Kepler-186f orbits.

"There are plenty of reasons to be optimistic that we will find hints of extraterrestrial life within the next few decades, just maybe not on an Earth-like planet around a Sun-like star."

So perhaps it's time to sell off that cryo chamber you've been prepping for a trip to Alpha Centauri or wherever and use the benefits to start building a football-field-sized space telescope to better locate our first future interstellar destination.

About the author

Crave freelancer Eric Mack is a writer, radio producer, and podcaster based in Taos, N.M., but he lives in Google+. He's also managing editor of Crowdsourcing.org and has written e-books on both Alaska and Android. E-mail Eric.
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